There are a number of different MRI equipment designs commercially available and depending upon the precise application, these designs will differ substantially as well as function in different ways.
For example, the present assignee has developed a number of different methods and apparatuses for performing functional magnetic resonance imaging (FMRI) in conscious animals. Assignee's U.S. Pat. No. 6,711,430, which is hereby incorporated by reference in its entirety, describes an exemplary apparatus for performing neuroimaging in conscious animals. While this apparatus offers excellent results for its intended use of performing neuroimaging in conscious animals, there are a number of challenges encountered in converting this technology to technology that can be used to construct a device that is suitable for use in human applications. Not only is there an issue of modifying electronics to handle the different electronic loads, etc.; but Applicants have discovered that there are also a number of structural modifications that have to be made to produce an improved working apparatus.
More specifically, as shown in FIG. 1, a prior conventional volume coil 10 set forth in the '430 patent, incorporated a design where the volume coil 10 was formed of a number of concentric cylindrical members including an inner cylinder (core module) 20 and a shield support cylinder 30 that is disposed concentrically about the inner cylinder 20. The inner cylinder 20 includes on its inner surface 22 a number of inner conductors (conductive strip lines) 24 that extend parallel to the longitudinal axis of the inner cylinder 20. In addition, the volume coil 10 has shielding 40 that overlies the inner cylinder 20. The shielding 40 is preferably in the form of strips that are supported by the support cylinder 30 and also extends parallel to the longitudinal axis of the inner cylinder 20. When the shielding 40 is in the form of strips, it defines a number of slots 42 between adjacent strips with a number of capacitors 50 being disposed therein at set locations. A pair of PCBs are provided.
While particularly suited for use with restrained animals, the volume coil 10 has a number of structural deficiencies that are apparent when attempting to modify for use in human MRI applications. For example, the inner conductive strip lines 24 are located on the inner surface of the inner cylinder (core module) 20 and therefore, these strip lines 24 (microstrip lines) are exposed to biological loads that can potentially disrupt or damage the electronic functioning of the apparatus. More specifically, if biological fluid comes into contact with the exposed microstrip lines 24, the electronics could potentially be damaged by such fluid. Also, the patient is inserted into the bore of the inner cylinder 20 and therefore, these microstrip lines 24 are in full view and are easily touchable by the patient. Once again, a patient, as a result of an accident or a traumatic claustrophobic event, might touch and potentially damage the exposed microstrip lines 24.
There are a number of other deficiencies that must be overcome in order to convert the apparatus of FIG. 1 into an operating apparatus intended for human head imaging with fields strengths of 1.5T, 3T, 4T and above.